It is well known that it is desirable to electronically secure data in certain types of electronic equipment. For example, antivirus or firewall software can operate on a computer to prevent unauthorized access to, and tampering with, secure data. In more complex computer systems, electronic security may also be provided by a cryptographic module, or gateway, which is typically deployed between the computer system and another potentially unsecured network, such as the Internet.
Certain markets further demand that electronic equipment also be physically secure. For example, the 140 series of Federal Information Processing Standards (FIPS) are United States government standards that specify computer security requirements for cryptography modules. FIPS 140-2, which is supplied in the Information Disclosure Statement (IDS) filed with this application, is the latest version of these standards and addresses cryptographic module security in wide range of applications and environments. Compliance with FIPS is required of cryptographic modules used by certain governmental agencies.
FIPS 140-2 specifies four levels of security, each with increasingly more stringent security requirements. Level 2, for example, specifies enhanced physical security mechanisms for a cryptographic module by requiring tamper evidence (e.g., tamper-evident coatings or seals; pick-resistant locks) which must be broken to attain physical access to the plain text cryptographic keys and critical security parameters within the module. Level 2 also generally requires a tamper-evident enclosure that is visually opaque.
Not all customers of cryptographic modules will require such physical security measures, such as some companies in the private sector. This leaves producers of cryptographic modules with difficult choices. A producer can make all cryptographic modules to the highest security standards even if such standard are not required by some customers. This is unfortunate, because physical security measures are generally more difficult and expensive to produce and thus increase the cost of the module, despite the fact that certain markets don't require these measures. Alternatively, the producers can make different cryptographic modules for different markets—i.e., more-physically-secure modules for government markets and less-physically-secure modules for private sector markets. But having to make essentially the same module two different ways is obviously not efficient for the producer.
Regardless, compliance with FIPS-style physical security requirements can be difficult to achieve. Cryptographic modules typically contain a number of open spaces to allow for airflow to cool internal circuitry during its operation. Due to FIPS's requirement of a visually opaque enclosure, such open spaces must be covered to some degree. This has the potential to increase heating in the module, which can adversely affect its operation.
Cost-effective and simple solutions to these problems are desired.